The present invention relates to image forming apparatus such as a digital copying machine or the like which stores image formation read out from a document in a memory as digital information and then forms a visible image on a recording sheet based on the stored digital information, and an image forming method used in the same image forming apparatus.
In a digital copying machine, since a visible image is formed on a recording sheet by use of digital image information once stored in a memory, if the digital information is formed by reading out a document image from a document, then the image can be formed on a desired number of sheets using such digital image information. Therefore, the digital copying machine is suitable to produce a plurality of copies of the document, especially, it is suitable to produce a plurality of copies of two or more sheets of documents, the digital copying machine is also able to process and output the stored digital image information with ease, and the digital copying machine is further able to exchange necessary image information with other image forming apparatus such as a facsimile, a printer or the like.
For these reasons, in recent years, use of such a digital copying machine has been started not only from the viewpoint of copying a plurality of copies of two or more sheets of documents but also from the viewpoint of establishing an on-line network with other image forming apparatus such as a facsimile, a printer or the like.
And, in such a digital copying machine, considering that an on-line network can be established for the formed digital image formation and also that, in the production of a plurality of copies of two or more sheets of documents, the first copy can be discharged as fast as possible, it is desired that the two or more sheets of documents may be read and processed in a so called 1.fwdarw.N order in which the items of the documents are read and processed sequentially from the 1st item thereof to the final or the N-th item.
On the other hand, in a use in which a plurality of copies must be produced from each of such two or more sheets of documents, the number of recording sheets copied and discharged out from the copying machine is large, which increases the amount of operation of post-processing operations such as a fold collecting operation, a stapling operation, a punching operation and other similar operations to thereby increase an operator's load. For this reason, there has been often added a post-processing device which is used to collect, staple and punch the folds of the recording sheets.
In such a post-processing device, from the viewpoint that an operator can replace staples efficiently as well as that the staples can be applied to recording sheets of different sizes properly, the stapling position of the staplers to be hit by a stapler must be specially set at a position which is situated on the body side of the copying machine and on the near side of the machine body to the operator. For this reason, in a copying machine to which such post-processing device is additionally attached, the recording sheets, which have been copied, must be discharged in such a manner that the stapling positions thereof are in agreement with the hitting positions of the stapled. For example, the recording sheets after being copied must be discharged such that, when the direction of discharge of the recording sheets is in the right direction of the copying machine body (a so called right discharge), the stapling positions of the recording sheets are situated on the right and near side (that is, on the right side and on the near side to the operator) of the copying machine body and, on the other hand, when the discharge direction of the recording sheets is in the left direction of the copying machine body (a so called left discharge), the stapling positions of the recording sheets are situated on the left and near side of the copying machine body to the operator.
Also, in the image forming means of the copying machine, as a technology relating to the transfer position of a visible image, that is, at which position of a latent image carrier such as a photoconductor drum, a photoconductor belt or the like the visible image is transferred onto the recording sheet, there are actually employed three kinds of transfer technologies: that is, a first technology in which the visible image is transferred at a position of 6 o'clock in the lower portion of the latent image carrier (bottom transfer technology); a second technology in which the visible image is transferred at a position of 9 o'clock (or 3 o'clock) situated laterally of the 6 o'clock position (side transfer technology); and, a third technology in which the visible image is transferred at a position of 12 o'clock situated upwardly of the 12 o'clock position (top transfer technology). However, in the side and top transfer technologies, there is required delivery means which delivers the recording sheet with the unfixed visible image carried thereon in the vertical direction, or delivers the recording sheet with the unfixed visible image carried on the lower surface side thereof during the time from transfer of the visible image to the recording sheet to fixing of the visible image. Also, since the unfixed visible image is easily damaged, the delivery means must be structured in a very complicated manner, which results in increased cost. In view of this, with respect to the transfer position of the present image forming means, considering the stability or reliability of the image quality or the delivery efficiency of the recording sheet after being transferred, it is preferred to employ the bottom transfer technology in which the visible image is transferred at the 6 o'clock position in the lower portion of the latent image carrier.
By the way, in this type of copying machine, the document to be copied varies in size and form, that is, it ranges widely from a very soft sheet type of document to a thick and rigid sheet type of document and further includes sheets of documents which have been bound into a book. Especially, the documents bound as a book cannot be delivered to the reading position of the document image by an automatic document feed device and, therefore, there is indispensable conventional type document reading means in which the documents are placed on a platen and are scanned for reading the images of the documents. These circumstances are quite the same in the digital copying machine as well.
For this reason, in the digital copying machine, in order to make good use of its strong point that it is suitable to make a large number of copies of numerous sheets of documents, it is desirable to employ automatic document feed and read means of a scan type which scans a sheet of document while the front and back of the document sheet are being naturally reversed to each other to thereby read the image of the document as digital image information. At the same time, it is also necessary to provide document read means which scans a document on a platen and reads the image of the document as digital image information. In this case, in order to make the best use of the strong point of the digital copying machine that the digital image information formed by reading the document image by means of the automatic document feed and read means can be combined with the digital image information read by the document read means to thereby edit them, it is desirable that the state of the digital image information to be formed by the document read means is matched with the state of the digital image information to be formed by the automatic document feed and read means.
Under these circumstances, the present inventors have studied carefully a digital copying machine which incorporates therein a scan type of automatic document feed and read means. In more particular, the present inventors have elaborately examined such digital copying machine in which, when the above-mentioned bottom transfer technology is employed as a technology relating to the transfer position of the image forming means thereof and also the above-mentioned post-processing device is additionally attached thereto, the recording sheet after being copied is discharged in such a manner that the staple position thereof is situated on "the body side and on the near side of the body of the copying machine" to the operator due to the condition relating to the hitting position of a staple by a stapler, when producing a plurality of copies of two or more sheets of documents, a document reading operation and a document image forming operation are carried out in parallel to thereby improve the efficiency of a copying processing operation so that the sheets of documents are read in the order of 1.fwdarw.N in which the first copy can be discharged earlier than other copies, and the digital image information to be formed by the above-mentioned automatic document feed and read means can be matched with the digital image information to be formed by the document read means.
In the process of careful study of the digital copying machine of the above type, the present inventors have found it possible to solve the above-mentioned problem by constructing the digital copying machine in the following structure: that is, in the automatic document feed and read means, a document, which is placed on the automatic document feed and read means in such a manner that the front surface of the document faces up and the top and bottom sides thereof are arranged correctly, is pulled in from above to be naturally reversed inside out in such a manner that the front and back surfaces of the document are reversed to each other, is then scanned in a forward or positive scan direction in which the document is moved from the left side of the present feed and read means to the right side thereof, whereby two or more sheets of documents can be read in the order of 1.fwdarw.N and the documents can be read in the form of digital image information having the same erect posture as the document images formed on the present documents; in the document read means which reads the document on the platen, the digital image information, which has been read and reversed in such a manner that the right and left sides thereof have been reversed to each other (that is, mirror image reversal), is output as it is to the image forming means; there is provided delivery means which allows the recording sheet to pass through the lower portion of the latent image carrier of the image forming means from the right side of the copying machine body to the left side thereof; and, there is employed a right discharge technique in which the recording sheet, after it is copied, is naturally reversed inside out and is discharged to the right side of the copying machine body. However, in such a digital copying machine, since it is necessary to discharge the recording sheet after being copied to the right side of the machine body while reversing it inside out naturally, the delivery path of the recording sheet becomes longer due to the natural reversal thereof. Also, it is difficult to set the recording sheet delivery path at a proper position, considering its relationship with respect to the latent image carrier of the image forming means, that is, from the viewpoint of design, it is difficult to employ such recording sheet delivery path.
In view of this, the present inventors have studied further and found it possible to solve the above problem by constructing the digital copying machine in the following structure: that is, in the automatic document feed and read means, a document, which is placed on the automatic document feed and read means in such a manner that the front surface of the document faces up and the top and bottom sides thereof are arranged correctly, is pulled in from above to be naturally reversed inside out such that the front and back surfaces of the document are reversed to each other, is scanned in a forward or positive scan direction in which the document is moved from the left side of the present feed and read means to the right side thereof, whereby two or more sheets of documents can be read in the order of 1.fwdarw.N and the documents can be read in the form of digital image information having the same erect posture as the document images formed on the present documents; in the document read means which reads the document on the platen, the digital image information that has been read thereby is output to the image forming means as the digital image information of the same erect posture as the digital image information that is finally formed by the automatic document feed and read means; there is employed a right discharge technique in which the recording sheet, after it is copied, is discharged to the right side of the copying machine body; and, in the recording sheet discharge operation, the recording sheet with a visible image fixed thereto is reversed inside out before the recording sheet is discharged.